Application of the genes coding for ribosomal RNA has been described in the oocytes of various species of organisms. Conceptually, amplification is characterized by the DNA coding for ribosomal RNA (the DNA within the nucleolus organizer), being duplicated many times in the absence of duplication of the remainder of the genome. Thus is produced a cell, the oocyte, in which the genes coding for ribosomal RNA are present in excess of their copy number in diploid somatic cells, while the genes comprising the remainder of the genome are present in the same copy number as they are in diploid somatic cells. Oocytes show striking differences with regard to the structure and function of organelles involved in ribosomal RNA synthesis (nucleoli). In order to determine whether gene amplification is a general phenomenon associated with oogenesis, the level of amplification of the genes coding for ribosomal RNA will be determined (1) in oocytes containing large masses of extrachromosomal nucleolus-associated DNA, (2) in oocytes in which such masses of DNA cannot be detected, (3) in oocytes which develop multiple nucleoli, (4) in oocytes in which the nucleolus remains singular throughout oogenesis, (5) in oocytes the nucleoli of which show little or no RNA synthetic activity, this function being carried out on the same oocytes in order to identify morphological characteristics of the amplified genes and their products. The objectives of the proposed research are to determine the extent of diversity which exists in regard to amplification of the genes coding for ribosomal RNA, and to correlate this diversity with differences in nucleolar structure and function.